I don't do scuba, but I shudder at the sight of those medieval torture devices all the same xD

Worse, that things like eqalization and decompression sickness were unknown back then.
The italian diver who located a sunken treasure had no eardrums left; and many workers who built the GoldenGate Bridge I think it was- died from decompression sickness.

No wonder the ancient freedivers, who accessed the ocen so freely and uninhibited, were mermaids in the eyes of ordinary people.